Welcome to The Visible Embryo
Home-- -History-- -Bibliography- -Pregnancy Timeline- --Prescription Drugs in Pregnancy- -- Pregnancy Calculator- --Female Reproductive System- -Contact

Welcome to The Visible Embryo, a comprehensive educational resource on human development from conception to birth.

The Visible Embryo provides visual references for changes in fetal development throughout pregnancy and can be navigated via fetal development or maternal changes.

The National Institutes of Child Health and Human Development awarded Phase I and Phase II Small Business Innovative Research Grants to develop The Visible Embryo. Initally designed to evaluate the internet as a teaching tool for first year medical students, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than one million visitors each month.

Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

WHO International Clinical Trials Registry Platform

The World Health Organization (WHO) has created a new Web site to help researchers, doctors and
patients obtain reliable information on high-quality clinical trials. Now you can go to one website and search all registers to identify clinical trial research underway around the world!




Pregnancy Timeline

Prescription Drug Effects on Pregnancy

Pregnancy Calculator

Female Reproductive System

Contact The Visible Embryo

News Alerts Archive

Disclaimer: The Visible Embryo web site is provided for your general information only. The information contained on this site should not be treated as a substitute for medical, legal or other professional advice. Neither is The Visible Embryo responsible or liable for the contents of any websites of third parties which are listed on this site.
Content protected under a Creative Commons License.

No dirivative works may be made or used for commercial purposes.


Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development
Google Search artcles published since 2007

Home | Pregnancy Timeline | News Alerts |News Archive Aug 13, 2014

Examples of each delineated white matter tract in specific male subjects.
Green: frontal tracts [critical tracts in social-emotional processing]
Blue: parietal-occipital tracts [sensory perception and multisensory integration]
Orange:temporal tracts.


WHO Child Growth Charts




Autism, Sensory Processing Disorders not the same

Groundbreaking research shows children with Sensory Processing Disorders have measureable brain differences from children with Autism Spectrum Disorders.

Researchers at the University of California San Francisco (UCSF) have found that children with Sensory Processing Disorders (SPD) have decreased structural brain connections in specific brain sensory regions different than those found in autism, further establishing SPD as a clinically important neurodevelopmental disorder.

Published in the journal PLOS ONE, this is the first study to compare structural connectivity in the brains of children with an Autism Spectrum Disorder (ASD) diagnosis, those with an SPD diagnosis, and compare both groups with typically developing boys. UCSF produced groundbreaking work in 2013 that found SPD boys have quantifiable regional differences in brain structure when compared to typically developing boys.

"With more than 1 percent of children in the U.S. diagnosed with an Autism Spectrum Disorder, and reports of 5 to 16 percent of children having Sensory Processing Difficulties, it's essential we define the neural underpinnings of these conditions, and identify where they overlap and where they are distinct," explains Pratik Mukherjee, MD, PhD, professor of radiology and biomedical imaging and bioengineering, UCSF, senior author.

"We are starting to catch up with what parents already knew; sensory challenges are real and can be measured both in the lab and in the real world. Our challenge is to find out why some children have SPD and move from our lab results to clinical application," says Elysa Marco MD, a child cognitive and behavioral neurologist at the UCSF Benioff Children's Hospital, and corresponding author.

SPD has not been listed in the Diagnostic and Statistical Manual used by psychiatrists and psychologists.

Children with SPD struggle with processing stimulation, which can cause a wide range of symptoms — hypersensitivity to sound, sight and touch, poor fine motor skills and easy distractibility. Some SPD children cannot tolerate the sound of a vacuum, others can't hold a pencil, some struggle with emotional regulation. Often, an irritating sound one day, can be tolerated the next.

The disorder can be baffling for parents and is a source of controversy for clinicians who debate whether it constitutes its own classification.

In the study, researchers used an advanced form of MRI called diffusion tensor imaging (DTI), to measure the movement of water molecules within the brain's white matter tracts. White matter forms the "wiring" linking different areas of the brain — essential to perceiving, thinking and action. DTI shows the direction of white matter fibers thereby mapping the structural connections between brain regions.

The study examined the connectivity of specific white matter tracts in16 SPD boys and 15 ASD boys between the ages of 8 and 12 — comparing them with 23 typically developing boys of the same ages.

Researchers found that both the SPD and ASD groups showed decreased connectivity in multiple parieto-occipital tracts — areas that handle basic sensory information in the back area of the brain.

However, only ASD children showed impairment in the inferior fronto-occipital fasciculi (IFOF), inferior longitudinal fasciculi (ILF), fusiform-amygdala and the fusiform-hippocampus tracts — critical tracts in social-emotion processing.

"One of the classic features of autism is decreased eye-to-eye gaze, and decreased ability to read facial emotions," said Marco. "Impairment in this region of brain connectivity not only differentiates ASD from SPD, but reflects the difficulties autistic patients have in the real world."

Kids with isolated SPD showed less connectivity in the basic perception and integration tracts that connect the auditory, visual and somatosensory (tactile) systems.

"Measuring a child's brain connectivity and function, gives us the ability to monitor if these connections are changing through clinical interventions," said Marco. "Larger studies to replicate this work are clearly needed, but we believe that DTI can be a powerful clinical tool for understanding sensory neurodevelopmental differences."

Over 90% of children with Autism Spectrum Disorders (ASD) demonstrate atypical sensory behaviors. In fact, hyper- or hyporeactivity to sensory input or unusual interest in sensory aspects of the environment is now included in the DSM-5 diagnostic criteria. However, there are children with sensory processing differences who do not meet an ASD diagnosis but do show atypical sensory behaviors to the same or greater degree as ASD children. We previously demonstrated that children with Sensory Processing Disorders (SPD) have impaired white matter microstructure, and that this white matter microstructural pathology correlates with atypical sensory behavior. In this study, we use diffusion tensor imaging (DTI) fiber tractography to evaluate the structural connectivity of specific white matter tracts in boys with ASD (n = 15) and boys with SPD (n = 16), relative to typically developing children (n = 23). We define white matter tracts using probabilistic streamline tractography and assess the strength of tract connectivity using mean fractional anisotropy. Both the SPD and ASD cohorts demonstrate decreased connectivity relative to controls in parieto-occipital tracts involved in sensory perception and multisensory integration. However, the ASD group alone shows impaired connectivity, relative to controls, in temporal tracts thought to subserve social-emotional processing. In addition to these group difference analyses, we take a dimensional approach to assessing the relationship between white matter connectivity and participant function. These correlational analyses reveal significant associations of white matter connectivity with auditory processing, working memory, social skills, and inattention across our three study groups. These findings help elucidate the roles of specific neural circuits in neurodevelopmental disorders, and begin to explore the dimensional relationship between critical cognitive functions and structural connectivity across affected and unaffected children.

The study's co-authors are Yi-Shin Chang, BSE, MS , Julia Owen, PhD, Shivani Desai, BS, Susanna Hill, BS, Anne Arnett, MA, and Julia Harris, BS, all of UCSF.

The research was supported by the Wallace Research Foundation, the Gates Family Foundation and the Holcombe Kawaja Family Foundation. The authors have reported that they have no conflicts of interest relevant to the contents of this paper to disclose.

UCSF is the nation's leading university exclusively focused on health. Now celebrating the 150th anniversary of its founding as a medical college, UCSF is dedicated to transforming health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care. It includes top-ranked graduate schools of dentistry, medicine, nursing and pharmacy; a graduate division with world-renowned programs in the biological sciences, a preeminent biomedical research enterprise and two top-tier hospitals, UCSF Medical Center and UCSF Benioff Children's Hospital San Francisco. Please visit http://www.ucsf.edu.

Return to top of page